EVALUATION OF RESILIENT MODULUS OF SUBGRADE AND GRANULAR LAYERS THROUGH FWD BASED ANALYSIS

Abstract

Resilient modulus of the layers is a key engineering property which is used in the design of the new pavement, as well as, while evaluating the existing pavement for possible rehabilitation. These are based on IRC:37 and IRC:115 in India. As per IRC guidelines, the resilient modulus of the subgrade is evaluated using an empirical correlation with its CBR value, and for the base course, it uses an empirical relationship with the thickness of the granular layer and the resilient modulus of the subgrade. According to global practice, this is a level-2 design approach. Level 1 approach considers the resilient modulus based on the laboratory test for analysis. Though the designs are based on resilient modulus of layers, the quality control during the construction stage is based on the examination of the density of a layer. In the absence of any standard relationship between density and resilient modulus this approach does not guarantee that the layer modulus is achieved. Therefore, this research work aims at arriving at the resilient modulus values of subgrade and granular layer using Falling Weight Deflectometer (FWD). When FWD is used during the construction stage, then the calculation of resilient modulus will allow the site engineer to take corrective measures if the modulus is find to be lower than desired. This will ensure the functionality of the pavement section throughout the design life. Subgrade modulus evaluated through FWD was in semblance with the IRC procedure with few location having difference in acceptable range . The granular layer modulus evaluated through IRC was found to be lower than the FWD analysis. The results look promising and indicate that the use of FWD is possible with certain modifications in the loading mechanism.